Paul Oxley - Ions and Collisions

Studies of charge transfer collisions between ions and atoms can play an important role in determining the properties of astrophysical plasmas. Collisions using protons and lithium atoms are also directly relevant to fusion plasma research since lithium atoms are injected into Tokamak plasmas to diagnose the plasma temperature and density. Below are pictures showing the ion source we use in the lab and some of the equipment which will be used for upcoming collision experiments.

Ions and Collisions
  • Colutron ion gun system. The ion gun consists of an ion source (an RF source from Beam Imaging Solutions on the left) focusing elements and a velocity filter. These latter parts are inside the 8" Conflat tee, and are also shown below.
  • The ion focusing elements on the left, and velocity filter on the right, removed from the vacuum system for repair.
  • View of the output end of the velocity filter when installed in the ion gun vacuum system. The filter uses a vertical magnetic field and a horizontal electric field to separate different ion species.
  • View from the rear of the ion gun system. This is an RF ion source which provides significantly more protons that our previous DC source.
  • Rear view of the electronics used to run the ion source.
  • The first ions from the RF ion source. 5mA of protons are registered by a Faraday cup ~6 inches from the exit of the ion gun.
  • Schematic of a charge-transfer collision experiment between protons and lithium atoms. After charge transfer the Li+ ions which result are steered by electric fields towards a channel electron multiplier (cone-shaped object, top right). The progress of the Li+ from the collision site to the electron multiplier are modelled in Simion.
  • Channel electron multiplier (CEM) which will be used to detect Li+ ions created in charge transfer collisions.
  • Li+ detection parts returned from the machine shop. The CEM will be housed inside one of the lower aluminium cylinders and the collisions will take place between the copper plates.
  • Chamber inside which the Li and ion beams will collide. The diameter of the top flange is 10 inches.
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